Background. Pacemaker or implantable cardiovascular-defibrillator (ICD) leads may be a primary cause of symptomatic tricuspid regurgitation (TR). The aim of this study was to evaluate the utility of 3-dimensional echocardiography (3-DE) in identifying intracardiac routes of pacemaker or ICD leads in relation to TR. Methods. 3-DE examinations were performed to evaluate intracardiac lead routes from right atrium to ventricle and positions at the tricuspid valve in 73 patients: 53 patients with pacemaker and 20 patients with ICD. TR severity was assessed by 2-dimensional echocardiography and classified as mild, moderate, or severe based on the ratio of TR area to right atrium area. Results 3-DE identified the lead route and position at the tricuspid valve in 68 patients (93.1%). In the remaining 5 patients, an appropriate image could not be obtained due to artifacts caused by the lead. TR severity was classified as mild in 47 patients, moderate in 18 patients, and severe in 8 patients. In 7 of the 8 patients with severe TR, obstruction to tricuspid valve closing caused by the lead was identified (Figure ): obstruction of septal leaflet in 3 patients, posterior leaflet in 3 patients, and anterior leaflet in 1 patient. However, in all patients with mild to moderate TR, the lead was positioned at the annulus side between leaflets, and no closing obstruction was identified. Conclusion. 3DE can identify pacemaker or ICD lead route and position at the tricuspid valve and the obstruction to closing caused by the lead in patients with severe TR. Therefore, 3DE may be useful to evaluate the cause of severe TR in patients receiving a pacemaker or ICD.